LiFePo4 vs Lead Acid...Some points of interest.

There are two straight lines--the constant current in Bulk at .25C in the one graph and the constant current in Bulk at .4C in the second graph. One takes four hours and the other takes one hour. How can that be?

If C is 100,

25a x 4h = 100AH and they haven't even started the Absorption stage yet.

40a x 1h = 40AH and then the 15 minute? Absorption stage gets the batt full to 100AH?

The fact that LiFePo4’s charge faster than Lead Acid can been substantiated per numerous industry papers (readily googled, ad nauseam...), and many credible personal accounts (RV.net)...Along with a near lack of voltage sag, long life and no maintenance, it’s this rapid charge characteristic that makes Lithium (and variants) the practical ‘elemental chemistry’ of choice for solar charged UPS power walls and regenerative braking in autos, and a worthy attribute at higher latitudes where peak harvest periods are often greatly limited...

3 tons, in the high Nevada Desert :)

time2roll wrote:

BFL13 wrote:
How do they get four times with .40C vs .25C?

Can anybody please explain? What am I missing?

The rate is a curve. There are no straight lines.

Your posted graph is a good representation.

The charging curve for LiFePo4 is pretty flat though.

I have a 12v 271 ah pack that I built for my truck camper and it's usually fully charged by the time lunch is finished, when there is full sun. It takes all day on a cloudy day. This is with 600 watts of solar panels.


I went from FLA to AGM to LFP. I'll never go back.

I've been away from this site for a while and came back to let everyone here know about some new Winston cells that are going for cheap. I'm not sure where to post about it or what the forum rules are so it would be nice if a mod gave me a little direction on that.

“I have a 12v 271 ah pack that I built for my truck camper and it's usually fully charged by the time lunch is finished, when there is full sun. It takes all day on a cloudy day. This is with 600 watts of solar panels.“

Though my system is a bit smaller than your’s (@200a/h LFP, 440w solar), the charge recovery advantage is substantial, and peak harvest times are considerably exploited - this attribute is pretty much a ‘settled science’ (per the principle of Occam’s razor...) and likely why NASA chose a Lithium variant for Mars Opportunity Rover’s energy reservoir...JMO

3 tons, in HarvestVille Central (e.g. the high NV Desert)

3 tons wrote:

Though my system is a bit smaller than your’s (@200a/h LFP, 440w solar), the charge recovery advantage is substantial, and peak harvest times are considerably exploited - this attribute is pretty much a ‘settled science’ (per the principle of Occam’s razor...) and likely why NASA chose a Lithium variant for Mars Opportunity Rover’s energy reservoir...JMO

3 tons, in HarvestVille Central (e.g. the high NV Desert)

Yeah I'm so happy with LFP and solar that I'm seriously considering getting rid of the generator and replacing that space with eight of those Winston cells for 1400 ah(or 16.8 Kilowatts). Two big problems with that, justifying it with my wife and timing. It's the wrong time of year for a big project like that. If this were the end of fall, I'd probably pull the trigger.

"Though my system is a bit smaller than your’s (@200a/h LFP, 440w solar), the charge recovery advantage is substantial,"

Solar charging rate goes up till noon then back down in a bell curve. 440W of solar can do about 30 amps at high noon, pick 20 amps average for a mid-morning to mid afternoon time? Hard to pick a charge rate with solar.

Say there is 200AH of SLA and 200AH of LFP getting 20 amps for however long so they are getting the same amount of sunshine at whatever rate for the comparison. Say both are down to 30% SOC (60AH) at the start.

Allow that the LFP does constant 20 amps to about 97% SOC, but the SLA tapers in the Absorption stage at a lower SOC. We know that 20 amps is a 10% charging rate on 200AH and that Bulk will go to 90% SOC (180AH) with the SLA before amps taper. (At a higher charging rate, Bulk would end at a lower SOC, making the LFP look better, but this is with the 440w and the 200AH.)

So 30-90 SOC = 180-60 =120AH at 20 amps = 6 hrs. So equal charging time for the first 6 hrs and now both batts are at 90% SOC (20AH left to go)

The "substantial recovery advantage" is all in the time it takes to do that last 20AH if you choose to go that high in SOC.

That would depend on your definition of "substantial".

Freep wrote:
I went from FLA to AGM to LFP. I'll never go back.

I've been away from this site for a while and came back to let everyone here know about some new Winston cells that are going for cheap. I'm not sure where to post about it or what the forum rules are so it would be nice if a mod gave me a little direction on that.

Here is a thread on building an LFP:

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/30223204

Post a link with your thoughts on the product for discussion.

Freep wrote:
Yeah I'm so happy with LFP and solar that I'm seriously considering getting rid of the generator and replacing that space with eight of those Winston cells for 1400 ah(or 16.8 Kilowatts).

Next RV for me might come with a broken generator so I can cry about the repairs to get a good price. Then just rip it out for space to put a monster battery.

“Can anybody please explain? What am I missing?”

Well, as a male I can’t experience pregnancy, yet after some considerable time at observation :) I can understand what it means - it’s in this light that ‘substantial’ means ‘more’...

3 tons

Gee, when a flashlight battery is almost exhausted its blub isn't bright like it was when the battery was new. Wow.